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draft-kuhn-nwcrg-network-coding-satellites-03.xml
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<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
<!ENTITY RFC2119 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml">
]>
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<?rfc compact="yes" ?>
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<rfc
category="info"
docName="draft-kuhn-nwcrg-network-coding-satellites-03"
ipr="trust200902">
<!-- category values: std, bcp, info, exp, and historic
ipr values: full3667, noModification3667, noDerivatives3667
you can add the attributes updates="NNNN" and obsoletes="NNNN"
they will automatically be output with "(if approved)" -->
<!-- ***** FRONT MATTER ***** -->
<front>
<!-- The abbreviated title is used in the page header - it is only necessary if the
full title is longer than 39 characters -->
<title abbrev="Network coding and satellites">Network coding and satellites</title>
<author role="editor" fullname="Nicolas Kuhn" initials="N" surname="Kuhn">
<organization>CNES</organization>
<address>
<postal>
<street>18 Avenue Edouard Belin</street>
<city>Toulouse</city>
<region></region>
<code>31400</code>
<country>France</country>
</postal>
<phone></phone>
<email>nicolas.kuhn@cnes.fr</email>
</address>
</author>
<author role="editor" fullname="Emmanuel Lochin" initials="E" surname="Lochin">
<organization>ISAE-SUPAERO</organization>
<address>
<postal>
<street>10 Avenue Edouard Belin</street>
<city>Toulouse</city>
<region></region>
<code>31400</code>
<country>France</country>
</postal>
<phone></phone>
<email>emmanuel.lochin@isae-supaero.fr</email>
</address>
</author>
<date month="February" year="2018" />
<!-- If the month and year are both specified and are the current ones, xml2rfc will fill
in the current day for you. If only the current year is specified, xml2rfc will fill
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necessary to specify at least a month (xml2rfc assumes day="1" if not specified for the
purpose of calculating the expiry date). With drafts it is normally sufficient to
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<area>Transport</area>
<workgroup>Internet Engineering Task Force</workgroup>
<!-- WG name at the upperleft corner of the doc,
IETF is fine for individual submissions.
If this element is not present, the default is "Network Working Group",
which is used by the RFC Editor as a nod to the history of the IETF. -->
<keyword>SATCOM, network coding</keyword>
<!-- Keywords will be incorporated into HTML output
files in a meta tag but they have no effect on text or nroff
output. If you submit your draft to the RFC Editor, the
keywords will be used for the search engine. -->
<!-- ######################################################-->
<!-- ######################################################-->
<!-- Head of the document -->
<!-- ######################################################-->
<!-- ######################################################-->
<abstract>
<t>This memo presents the current deployment of network coding in some satellite telecommunications systems along with a discussion on the multiple opportunities to introduce these techniques at a wider scale.</t>
</abstract>
</front>
<middle>
<section anchor="sec:introduction" title="Introduction">
<t>Network coding schemes are inherent part of the satellite systems as the physical layer requires specific robustness to guarantee an efficient usage of the expensive radio resource. Further exploiting these schemes is an opportunity for a better end-user experience along with a better exploitation of the scarce resource.</t>
<t>In this context, this memo aims at:</t>
<t><list style="symbols">
<t>summing up the current deployment of network coding schemes over LEO and GEO satellite systems;</t>
<t>identifying opportunities for further usage of network coding in these systems.</t>
</list></t>
<section anchor="subsec:intro_glossary" title="Glossary">
<t>The glossary of this memo is related to the network coding taxonomy document <xref target="I-D.irtf-nwcrg-network-coding-taxonomy"> </xref>.</t>
<t>The glossary is extended as follows:<list style="symbols">
<t>BBFRAME: Base-Band FRAME;</t>
<t>PLFRAME: Physical Layer FRAME;</t>
<t>PEP: Performance Enhanced Proxy;</t>
<t>SATCOM: SATellite COMmunications;</t>
<t>EPC: Evolved Packet Core;</t>
<t>UMTRAN: Universal Mobile Terrestrial Radio Access Network;</t>
<t>QoS: Quality-of-Service;</t>
<t>QoE: Quality-of-Experience;</t>
<t>VNF: Virtualized Network Function;</t>
<t>CPE: Customer Premise Equipment;</t>
<t>ETSI: European Telecommunications Standards Institute;</t>
<t>DTN: Delay Tolerant Network.</t>
</list></t>
</section>
<section anchor="subsec:intro_requi" title="Requirements Language">
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in <xref target="RFC2119">RFC 2119</xref>.</t>
</section>
</section>
<!-- ######################################################-->
<!-- ######################################################-->
<!-- Body of the document -->
<!-- ######################################################-->
<!-- ######################################################-->
<!-- ######################################################-->
<!-- New section -->
<!-- ######################################################-->
<section anchor="sec:sat_topo" title="A note on satellite topology">
<t>The objective of this section is to provide both a generic description of the components composing a generic satellite system and their interaction. It provides a high level description of a multi-gateway satellites network. There exist multiple SATCOM systems, such as those dedicated to broadcasting TV or to IoT applications: depending on the purpose of the SATCOM system, ground segments are specific. This memo lays on SATCOM systems dedicated to Internet access that follows the DVB-S2/RCS2 standards.</t>
<t>In this context, <xref target="fig:sat_gateway"></xref> shows an example of a multigateway satellite system. More details on a generic SATCOM ground segment architecture for a bi-directional Internet access can be found in <xref target="SAT2017"></xref>. </t>
<t>It is worth noting that some functional blocks aggregate the traffic coming from multiple users, allowing the deployment of network coding schemes. </t>
<figure anchor="fig:sat_gateway" title="Data plane functions in a generic satellite multi-gateway system">
<artwork>
+---------------------+
| Application servers |
+---------------------+
| | |
| | |
-----------------------------------
v v v v v v
+------------------+ +------------------+
| network function | | network function |
| (firewall, PEP) | | (firewall, PEP) |
+------------------+ +------------------+
| | | |
| | IP packets | |
v v v v
+------------------+ +------------------+
| access gateway | | access gateway |
+------------------+ +------------------+
| |
| BBFrames |
v v
+------------------+ +------------------+
| physical gateway | | physical gateway |
+------------------+ +------------------+
| |
| PLFrames |
v v
+------------------+ +------------------+
| outdoor unit | | outdoor unit |
+------------------+ +------------------+
| | | |
| | Satellite link | |
v v v v
+------------------+ +------------------+
| sat terminals | | sat terminals |
+------------------+ +------------------+
</artwork>
</figure>
</section>
<!-- ######################################################-->
<!-- New section -->
<!-- ######################################################-->
<section anchor="sec:existing_network_coding" title="Status of network coding in actually deployed satellite systems">
<t> </t>
<t><xref target="fig:existing_network"></xref> presents the status of the network coding deployment in satellite systems. The information is based on the taxonomy document <xref target="I-D.irtf-nwcrg-network-coding-taxonomy"> </xref> and the notations are the following: End-to-End Coding (E2E), Network Coding (NC), Intra-Flow Coding (IntraF), Inter-Flow Coding (InterF), Single-Path Coding (SP) and Multi-Path Coding (MP).</t>
<t>X1 embodies the source coding that could be used at application level for instance: for video streaming on a broadband access. X2 embodies the physical layer, applied to the PLFRAME, to optimize the satellite capacity usage. Furthermore, at the physical layer and when random accesses are exploited, FEC mechanisms are exploited.</t>
<figure anchor="fig:existing_network" title="Network coding and satellite systems">
<artwork>
+------+-------+---------+---------------+-------+
| | Upper | Middle | Communication layers |
| | Appl. | ware | |
+ +-------+---------+---------------+-------+
| |Source | Network | Packetization | PHY |
| |coding | AL-FEC | UDP/IP | layer |
+------+-------+---------+---------------+-------+
|E2E | X1 | | | |
|NC | | | | |
|IntraF| X1 | | | |
|InterF| | | | X2 |
|SP | X1 | | | X2 |
|MP | | | | |
+------+-------+---------+---------------+-------+
</artwork>
</figure>
</section>
<!-- ######################################################-->
<!-- New section -->
<!-- ######################################################-->
<section anchor="sec:use_cases" title="Details on the use cases">
<t>This section details use-cases where network coding schemes could improve the overall performance of a SATCOM system (e.g. considering a more efficient usage of the satellite resource, delivery delay, delivery ratio).</t>
<t>It is worth noting that these use-cases focus more on the middle ware (e.g. aggregation nodes) and packetization UDP/IP of <xref target="fig:existing_network"></xref>. Indeed, there are already lots of recovery mechanisms at the physical and access layers in currently deployed systems while E2E source coding are done at the application level. In a multigateway SATCOM Internet access, the specific opportunities are more relevant in specific SATCOM components such as the "network function" block or the "access gateway" of <xref target="fig:sat_gateway"></xref>.</t>
<section anchor="subsec:two-way" title="Two way relay channel mode">
<t>This use-case considers a two-way communication between end users, through a satellite link. We propose an illustration of this scenario in <xref target="fig:two_way"></xref>.</t>
<t>Satellite terminal A (resp. B) transmits a flow A (resp. B) to a server hosting NC capabilities, which forward a combination of the two flows to both terminals. This results in non-negligible bandwidth saving and has been demonstrated at ASMS 2010 in Cagliari <xref target="ASMS2010"></xref>. Moreover, with On-Board Processing satellite payloads, the network coding operations could be done at the satellite level, thus reducing the end-to-end delay of the communication.</t>
<figure anchor="fig:two_way" title="Network architecture for two way relay channel with NC">
<artwork>
+------------+ +-----+ +---------+
| Satellite | A | | A | |
| Terminal A |-->--| | |->---| | +------+
+------------+ | | |->---| | | |
|| A+B ->-| SAT | B | Gateway | | |
==================| | | |--|Server|
|| ->-| | | | | |
+------------+ B |>-| |=====| | | |
| Satellite |-->--| | | A+B | | +------+
| Terminal B | | | | |
+------------+ +-----+ +---------+
</artwork>
</figure>
</section>
<section anchor="subsec:rel-mul" title="Reliable multi-cast">
<t>This use-case considers adding redundancy to a multi-cast flow depending on what has been received by different end-users, resulting in non-negligible scarce resource saving. We propose an illustration for this scenario in <xref target="fig:rel_multi"></xref>.</t>
<t>A multi-cast flow (M) is forward to both satellite terminals A and B. On the uplink, terminal A (resp. B) does not acknowledge the packet Ni (resp. Nj) and either the access gateway or the multi-cast server includes the missing packets in the multi-cast flow so that the information transfer is reliable. This could be achieved by using NACK-Oriented Reliable Multicast (NORM) <xref target="RFC5740"></xref>. However, NORM does not consider other network coding schemes such as sliding window encoding described in <xref target="I-D.irtf-nwcrg-network-coding-taxonomy"></xref>.</t>
<figure anchor="fig:rel_multi" title="Network architecture for a reliable multi-cast with NC">
<artwork>
+------------+ +-----+ +---------+
| Satellite |NACK Ni | |NACK Ni| |
| Terminal A |-->--| | |->-----| | +------+
+------------+ | | |->-----| | | |
|| M ->-| SAT |NACK Nj| | |Multi |
==================| | | Gateway |--|Cast |
|| ->-| | | | |Server|
+------------+ |>-| |=======| | | |
| Satellite |-->--| | | M | | +------+
| Terminal B |NACK Nj | | | |
+------------+ +-----+ +---------+
</artwork>
</figure>
</section>
<section anchor="subsec:hybrid" title="Hybrid access">
<t>This use-case considers the use of multiple path management with network coding at the transport level to either increase the reliability or the total bandwidth. We propose an illustration for this scenario in <xref target="fig:hyb_access"></xref>. This use-case is inspired from the Broadband Access via Integrated Terrestrial Satellite Systems (BATS) project and has been published as an ETSI Technical Report <xref target="ETSITR2017"></xref>. It is worth nothing that this kind of architecture is also discussed in the MPTCP working group <xref target="I-D.boucadair-mptcp-dhc"></xref>.</t>
<t>To cope from packet loss (due to either end-user movements or physical layer impairments), network coding could be introduced in both the CPE and at the concentrator.</t>
<figure anchor="fig:hyb_access" title="Network architecture for an hybrid access using NC">
<artwork>
+-------------+ +----------------+
|->| SAT NETWORK |---| BACKBONE |
| +-------------+ | +------------+ |
+------+ | | |CONCENTRATOR| |
| CPE |-->-| +-----+ | +------------+ |
+------+ |->| DSL |-----------| |
| +-----+ | |
| | |
| +-----+ | |
|->| LTE |-----------| |
+-----+ +----------------+
</artwork>
</figure>
</section>
<section anchor="subsec:dtn" title="Delay Tolerant Network architecture">
<t>** EL: ** TBD with bundle layer as a candidate for NC</t>
</section>
<section anchor="subsec:varying" title="Dealing with varying capacity">
<t>This use-case considers the usage of network coding to overcome cases where the wireless link characteristics quickly change overtime and where the physical layer codes could not be made robust in time. This is particularly relevant when end users are moving and the channel shows important variations <xref target="IEEEVT2001"></xref>.</t>
<t>The architecture is recalled in <xref target="fig:varying_capa"></xref>. The network coding schemes could be applied at the access gateway or the network function block levels to increase the reliability of the transmission. This use-case is mostly relevant for when mobile users are considered or when the chosen band induce a required physical layer coding that may change over time (Q/V bands, Ka band, etc.).</t>
<figure anchor="fig:varying_capa" title="Network architecture for dealing with varying link characteristics with NC">
<artwork>
+------------+ +-----+ +---------+ +--------+ +---------+
| Satellite | | SAT | | Physical| | Access | | Network |
| Terminal |->| |->| gateway |->| gateway|->| function|
+------------+ +-----+ +---------+ +--------+ +---------+
NC? NC NC? NC?
</artwork>
</figure>
</section>
<section anchor="subsec:gat_hand" title="Improving the gateway handovers">
<t>This use-case considers the recovery of packets that may be lost during gateway handovers. Whether this is for off-loading one given equipment or because the transmission quality is not the same on each gateway, changing the transmission gateway may be relevant. However, if gateways are not properly synchronized, this may result in packet loss. During these critical phases, network coding can be added to improve the reliability of the transmission and propose a seamless gateway handover.</t>
<t>An example architecture for this use-case is showed in <xref target="fig:gat_hand"></xref>. It is worth noting that depending on the ground architecture <xref target="I-D.chin-nfvrg-cloud-5g-core-structure-yang"> </xref><xref target="SAT2017"></xref>, some equipments might be communalised.</t>
<figure anchor="fig:gat_hand" title="Network architecture for dealing with gateway handover schemes with NC">
<artwork>
+---------+ +--------+ +---------+
| Physical| | Access | | Network |
----->| gateway |->| gateway|->| function|
| +---------+ +--------+ +---------+
v | |
+------------+ +-----+ +-------------+
| Satellite | | SAT | | Switching |
| Terminal |->| | | Entity |
+------------+ +-----+ +-------------+
^ | |
| +---------+ +--------+ +---------+
----->| Physical| | Access | | Network |
| gateway |->| gateway|->| function|
+---------+ +--------+ +---------+
</artwork>
</figure>
</section>
</section>
<!-- ######################################################-->
<!-- New section -->
<!-- ######################################################-->
<section anchor="sec:deploy" title="Discussion on the deployability">
<t>This section discusses the deployability of the use-cases detailed in <xref target="sec:use_cases"></xref>.</t>
<t>SATCOM systems typically feature Proxy-Enhanced-Proxy <xref target="RFC3135">RFC 3135</xref> which could be relevant to host network coding mechanisms and thus support the use-cases that have been discussed in <xref target="sec:use_cases"></xref>. In particular the discussion on how network coding can be integrated inside a PEP with QoS scheduler has been proposed in <xref target="RFC5865">RFC 5865</xref>.</t>
<t>The generic architecture proposed in <xref target="fig:sat_gateway"></xref> may be mapped to cellular networks as follows: the 'network function' block gather some of the functions of the Evolved Packet Core subsystem, while the 'access gateway' and 'physical gateway' blocks gather the same type of functions as the Universal Mobile Terrestrial Radio Access Network. This mapping extends the opportunities identified in this draft since they may be also relevant for cellular networks.</t>
<t> Related to the foreseen virtualized network infrastructure, the network coding schemes could be proposed as VNF and their deployability enhanced. The architecture for the next generation of SATCOM ground segments would rely on a virtualized environment. This trend can also be seen, making the discussions on the deployability of network coding in SATCOM extendable to other deployment scenarios <xref target="I-D.chin-nfvrg-cloud-5g-core-structure-yang"> </xref>. As one example, the network coding VNF functions deployment in a virtualized environment is presented in <xref target="I-D.vazquez-nfvrg-netcod-function-virtualization"> </xref>.</t>
</section>
<!-- ######################################################-->
<!-- ######################################################-->
<!-- Tail of the document -->
<!-- ######################################################-->
<!-- ######################################################-->
<section anchor="sec:acknowledgements" title="Acknowledgements">
<t>Many thanks to Tomaso de Cola, Vincent Roca and Marie-Jose Montpetit.</t>
</section>
<section anchor="sec:contributors" title="Contributors">
<t>Tomaso de Cola, Vincent Roca, Marie-Jose Montpetit.</t>
</section>
<section anchor="sec:IANA" title="IANA Considerations">
<t>This memo includes no request to IANA.</t>
</section>
<section anchor="sec:ecurity" title="Security Considerations">
<t>This document, by itself, presents no new privacy nor security issues.<!--See <xref target="RFC3552">RFC 3552</xref> for a guide.--></t>
</section>
</middle>
<!-- *****BACK MATTER ***** -->
<back>
<!-- References split into informative and normative -->
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<references title="Normative References">
&RFC2119;
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<references title="Informative References">
<?rfc include="reference.RFC.3135.xml"?>
<?rfc include="reference.RFC.5865.xml"?>
<?rfc include="reference.RFC.5740.xml"?>
<?rfc include="reference.I-D.irtf-nwcrg-network-coding-taxonomy.xml"?>
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<reference anchor="ETSITR2017">
<front>
<title>Satellite Earth Stations and Systems (SES); Multi-link routing scheme in hybrid access network with heterogeneous links </title>
<author initials="" surname="">
</author>
<date year="2017" />
</front>
<seriesInfo name="ETSI TR" value="103 351" />
</reference>
<reference anchor="ASMS2010">
<front>
<title>Demonstration at opening session of ASMS 2010</title>
<author initials="T" surname="De Cola">
</author>
<author initials="et" surname="al.">
</author>
<date year="2010" />
</front>
<seriesInfo name="ASMS" value="" />
</reference>
<reference anchor="IEEEVT2001">
<front>
<title>Statistical modeling of the LMS channel</title>
<author initials="F.P" surname="Fontan">
</author>
<author initials="M" surname="Vazquez-Castro">
</author>
<author initials="C.E" surname="Cabado">
</author>
<author initials="J.P" surname="Garcia">
</author>
<author initials="E" surname="Kubista">
</author>
<date year="2001" />
</front>
<seriesInfo name="IEEE Transactions on Vehicular Technology" value="vol. 50 issue 6" />
</reference>
<reference anchor="SAT2017">
<front>
<title>Software-defined satellite cloud RAN</title>
<author initials="T" surname="Ahmed">
</author>
<author initials="E" surname="Dubois">
</author>
<author initials="JB" surname="Dupe">
</author>
<author initials="R" surname="Ferrus">
</author>
<author initials="P" surname="Gelard">
</author>
<author initials="N" surname="Kuhn">
</author>
<date year="2017" />
</front>
<seriesInfo name="Int. J. Satell. Commun. Network." value="vol. 36" />
</reference>
</references>
</back>
</rfc>